Academic literature on the topic 'Truss lattice'

Heterogeneous lattice structure was constructed with rhombic dodecahedron and octet-truss lattice structures. The rhombic dodecahedron lattice was bending-dominated, while octet-truss lattice was stretching-dominated. The rhombic dodecahedron lattice fabricated by selective laser melting (SLM) was compressed by a universal testing machine, which was also investigated by finite element model. Afterwards, the validated numerical model was used to study the designed heterogeneous lattice. Calculations indicates that heterogeneous lattice structures outperform the rhombic dodecahedron lattice structure. The introduction of octet-truss unit cell enhances the mechanical behavior of the heterogeneous lattice structure in terms of Young’s modulus and stress magnitude, which depends on the pattern of octet-truss cells.

Purpose This paper aims to present a multiscale fuzzy optimization (FO) method to optimize both the density distribution and macrotopology of a uniform octet-truss lattice structure. Design/methodology/approach The design formulae for the strut radii are presented based on the effective mechanical properties obtained from the representative volume element. The proposed basic lattice material is applied in a normalization process to determine the material model with penalization. The solid isotropic material with penalization (SIMP) method is extended to solve the minimum compliance problem using the optimality criteria. The evolutionary deletion process is proposed to delete elements corresponding to thin-strut unit cells and to obtain the optimal macrotopology. Findings Both numerical cases indicate that the FO results significantly improved in structural performance compared with the results of the conventional SIMP. The deleting threshold controls the macrotopology of the graded-density lattice structures with negligible effects on the mechanical properties. Originality/value This paper presents one of the first multiscale optimization methods to optimize both the relative density and macrotopology of uniform octet-truss lattices. The material model and corresponding optimality criteria of octet-truss lattices are proposed and implemented in the optimization.

The dynamic equivalent continuum model of beamlike space deployable lattice truss which is repetition of the basic truss bay is established based on the energy equivalence. The finite element model of the lattice truss is also developed. Free vibration frequencies and mode shapes are calculated and simulated based on equivalent continuum model and discrete finite element model. The analytical solutions calculated by equivalent continuum model match well with the finite element model simulation results. A prototype of deployable lattice truss consist of 20 truss bays is manufactured. The dynamic response of lattice truss with different truss bays are tested by dynamic vibration experiment, and natural frequencies of lattice truss with different length are obtained from acceleration response curves. The experiment results are compared with simulation results which verifies that the correctness of finite element model, which also validate the effectiveness of equivalent continuum model indirectly.

Topological-reinforcement and material-strengthening were used and employed to improve the mechanical properties of lattice truss sandwich structures. This new type of three-dimensional aluminum alloy lattice truss (named enhanced lattice truss) sandwich structure, with a relative density ranging from 1.7% to 4.7%, was designed and fabricated by interlocking and vacuum-brazing method. The out-of-plane compression and shear properties of the enhanced lattice truss sandwich structures (both as-brazed and age-hardened cores) were experimentally and analytically investigated. Good correlations between analytical predictions and experiment results were achieved. Experimental results showed that the mechanical properties of the enhanced lattice truss cores were sensitive to the unit-cell size and parent-alloy properties (i.e. inelastic buckling and tangential modulus). The compressive and shear characteristics of enhanced lattice truss sandwich structures were discussed and found superior to competing lattice truss structures in low density area (0.046–0.124 g/cm3) of material property charts. The combination of topological-reinforcement and material-strengthening provided a way to achieve lightweight sandwich structures with high specific strengths and low densities.

AbstractThis paper uses finite element method and neutron diffraction measurement to study the residual stress in lattice truss sandwich structure. A comparison of residual stress and thermal deformation between X-type and pyramidal lattice truss sandwich structure has been carried out. The residual stresses are concentrated in the middle joint and then decreases gradually to both the ends. The residual stresses in the X-type lattice truss sandwich structure are smaller than those in pyramidal structure. The maximum longitudinal and transverse stresses of pyramidal structure are 220 and 202 MPa, respectively, but they decrease to 190 and 145 MPa for X-type lattice truss sandwich structure, respectively. The thermal deformation for lattice truss sandwich panel structure is of wave shape. The X-type has a better resistance to thermal deformation than pyramidal lattice truss sandwich structure. The maximum wave deformation of pyramidal structure (0.02 mm) is about twice as that of X-type (0.01 mm) at the same brazing condition.

Abstract In recent years, lattice sandwich structures with truss-cores have shown great potential in lightweight, high load-bearing and multifunctional applications. However, there is still a lack of research on the vibration attenaution characteristics of such structures. In this paper, combined with the design concept of elastic metamaterial with the lattice truss-core sandwich structures, a meta-lattice sandwich structure with double-layer pyramidal truss core is proposed to realize superior vibration attenuation performance. Theoretical and numerical investigations are conducted on the bandgap mechanisms of the proposed meta-lattice structures. The efficient vibration suppression within the bandgap range is verified by numerical simulations. The results of this paper are of reference value for the design and engineering application of the lattice truss structure for vibration attenuation.

Abstract In recent years, lattice sandwich structures with truss-cores have shown great potential in lightweight, high load-bearing and multifunctional applications. However, there is still a lack of research on the vibration attenaution characteristics of such structures. In this paper, combined with the design concept of elastic metamaterial with the lattice truss-core sandwich structures, a meta-lattice sandwich structure with double-layer pyramidal truss core is proposed to realize superior vibration attenuation performance. Theoretical and numerical investigations are conducted on the bandgap mechanisms of the proposed meta-lattice structures. The efficient vibration suppression within the bandgap range is verified by numerical simulations. The results of this paper are of reference value for the design and engineering application of the lattice truss structure for vibration attenuation.

In this study, the effect of high temperature on the mechanical performance of CoCrNi medium-entropy alloy octet-truss lattice material fabricated via laser powder bed fusion (LPBF) is investigated by compressive test and numerical simulation method. The results reveal that the strength and energy absorption performance of CoCrNi octet-truss lattice material with a hollow truss are higher than those of ones with a solid truss; however, they diminish by 30% and 50%, respectively, as temperature rises from 25 °C to 600 °C. As the temperature rises, the potential barrier for dislocation slip decreases, making it easier for dislocations to move at high temperatures and thus reducing the strength. CoCrNi octet-truss lattice materials present the failure mechanism of progressive collapse at varied temperatures. Meanwhile, the mechanical performance of the experimental testing agreed well with numerical simulation results. The numerical results show that the strength and energy absorption properties of the CoCrNi lattice materials increase as the relative density, however, decreases with increasing temperature. Additionally, CoCrNi octet-truss lattice materials maintain exceptional energy absorption performance at varied temperatures.

Sandwich panels are extensively used in constructional, naval and aerospace structures due to their high stiffness and strength-to-weight ratios. In contrast, sound transmission properties of sandwich panels are adversely influenced by their low effective mass. Phase velocity matching of structural waves propagating within the panel and the incident pressure waves from the surrounding fluid medium lead to coincidence effects (often within the audible range) resulting in reduced impedance and high sound transmission. Truss-like lattice cores with porous microarchitecture and \emph{reduced} inter panel connectivity relative to honeycomb cores promise the potential to satisfy the conflicting structural and vibroacoustic response requirements. This study combines Bloch-wave analysis and the Finite Element Method (FEM) to understand wave propagation and hence sound transmission in sandwich panels with a truss lattice core. Three dimensional coupled fluid-structure finite element simulations are conducted to compare the performance of a representative set of lattice core topologies. Potential advantages of sandwich structures with a lattice core over the traditional shear wall panel designs are identified. The significance of partial band gaps is evident in the sound transmission loss characteristics of the panels studied. This work demonstrates that, even without optimization, significant enhancements in STL performance can be achieved in truss lattice core sandwich panels compared to a traditional sandwich panel employing a honeycomb core under constant mass constraint.<br>Applied Science, Faculty of<br>Mechanical Engineering, Department of<br>Graduate

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, February 2010.<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Cataloged from student submitted PDF version of thesis.<br>Includes bibliographical references.<br>The Town lattice truss is proposed as an appropriate technology for the Tshumbe Diocese of the Democratic Republic of Congo. This proposal is made based on an understanding of rural transport and appropriate technology and an in-depth analysis of the details of the Town lattice truss. The nature and importance of rural transport and accessibility are presented, and bridges are identified as a key component in rural transport development. The concept of appropriate technology is presented along with a framework consisting of required and desired characteristics of any appropriate technology, including bridges. Structural materials are compared for use in bridges in rural areas of developing countries and timber is selected as the appropriate choice for the Tshumbe Diocese. Three existing timber bridges systems for developing countries are analyzed and compared, and the Town lattice truss is proposed as an alternative to all three. The Town lattice truss is presented and described in detail with reference to a study of forty existing bridges in the northeastern United States that was conducted as a part of this work. Appropriate characteristics of the truss are identified and used to compare the truss with other timber bridge systems. The wooden pegged connections and chord structure are identified as unique components of the Town lattice truss and are the subjects of further analysis. Equations are developed for strength prediction and stiffness estimation for the wooden pegged connections.<br>(cont.) The chord structure is analyzed for strength and stiffness, which are determined to be combinations of underlying component properties based on the chord termination pattern that is used. A comprehensive set of possible chord termination patterns is developed and the best patterns are proposed for use in design. Finally, truss moment capacity is determined as a function of chord strength and stiffness properties and a simple methodology is proposed for the design of new Town lattice truss bridges.<br>by Todd Craig Radford.<br>Ph.D.

Cellular materials, often called lattice materials, are increasingly receiving attention for their ultralight structures with high specific strength, excellent impact absorption, acoustic insulation, heat dissipation media and compact heat exchangers. In alignment with emerging additive manufacturing (AM) technology, realization of the structural applications of the lattice materials appears to be becoming faster. Considering the direction dependent material properties of the products with AM, by directionally dependent printing resolution, effective moduli of lattice structures appear to be directionally dependent. In this paper, a constitutive model of a lattice structure, which is an octet-truss with a base material having an orthotropic material property considering AM is developed. In a case study, polyjet based 3D printing material having an orthotropic property with a 9% difference in the principal direction provides difference in the axial and shear moduli in the octet-truss by 2.3 and 4.6%. Experimental validation for the effective properties of a 3D printed octet-truss is done for uniaxial tension and compression test. The theoretical value based on the micro-buckling of truss member are used to estimate the failure strength. Modulus value appears a little overestimate compared with the experiment. Finite element (FE) simulations for uniaxial compression and tension of octet-truss lattice materials are conducted. New effective properties for the octet-truss lattice structure are developed considering the observed behavior of the octet-truss structure under macroscopic compression and tension trough simulations.

The advances in additive manufacturing removed most of the limitations that were once stopping designers when it comes to the manufacturability of the design. It allowed designers to produce parts with high geometric complexity such as cellular structures. These structures are known for their high strength relative to their low mass, good energy absorption, and high thermal and acoustic insulation compared to their relative solid counter-parts. Lattice structures, a type of cellular structures, have received considerable attention due to their properties when producing light-weight with high strength parts. The design of these structures can pose a challenge to designers due to the sheer number of variables that are present. Traditional optimization approaches become an infeasible approach for designing them, which motivated researchers to search for other alternative approaches. In this research, a new method is proposed by utilizing the material density information obtained from the topology optimization of continuum structures. The efficacy of the developed method will be compared to existing methods, such as the Size Matching and Scaling (SMS) method that combines solid-body analysis and a predefined unit-cell library. The proposed method shows good potential in structures that are subjected to multiple loading conditions compared to SMS, which would be advantageous in creating reliable structures. In order to demonstrate the applicability of the proposed method to practical engineering applications, the design problem of a commercial elevator sling will be considered.

Advances in additive manufacturing technologies have brought a new paradigm shift to both design and manufacturing. There is a much bigger design space in which designers can achieve a level of complexity and customizability, which are infeasible using traditional manufacturing processes. One application of this technology is for fabrication of meso-scale lattice structures (MSLS). These types of structures are designed to have material where it is needed for specific applications. They are suitable for any weight-critical applications, particularly in industries where both low weight and high strength are desired. MSLS can easily have hundreds to thousands of individual strut, where the diameter of each strut can be treated as a design variable. As a result, the design process poses a computational challenge. Since the computational complexity of the design problem often scales exponentially with the number of design variables, topological optimization that requires multi-variable optimization algorithm is infeasible for large-scale problems. In previous research, a new method was presented for efficiently optimizing MSLS by utilizing a heuristic that reduces the multivariable optimization problem to a problem of only two variables. The method is called the Size Matching and Scaling (SMS) method, which combines solid-body analysis and predefined unit-cell library to generate the topology of the structure. However, the method lacks a systematic methodology to generate the initial ground geometry for the design process, which limits the previous implementations of the SMS method to only simple, axis-aligned structures. In this research, an augmented SMS method is presented. The augmented method includes the integration of free-mesh approach in generating the initial ground geometry. The software that embodies that ground geometry generation process is integrated to commercial CAD system that allows designer to set lattice size parameters through graphical user interface. In this thesis, the augmented method and the unit-cell library are applied to various design examples. The augmented SMS method can be applied effectively in the design of conformal lattice structure with highly optimized stiffness and volume for complex surface. Conformal lattice structures are those conformed to the shape of a part's surface and that can used to stiffen or strengthen a complex and curved surface. This design approach removes the need for a rigorous topology optimization, which is a main bottleneck in designing MSLS.

This thesis discusses how to test the mechanical properties of openlattice truss structures and hybrids being a tube containing a latticetruss structure. By properties we mean strength, stiffness, thermalconductivity and so forth.Mechanical testing was done on two different structures to betterunderstand how the load-bearing properties change when these structuresare subjected to tensile, compressive and bending forces. The structuresinvestigated were Diamond and Octagon built at 45° and 90°. Acousticemission was also used to evaluate and analyze the different behaviour ofthe structures. The test results were used to produce design criteria forproperties in different cell structures manufactured of Hastelloy X™. Amap with design criteria containing stiffness and weight per cubiccentimetre was produced for parts that would be subjected to compressiveforces.

Fracture mechanics plays an important role in the material science, structure design and industrial production due to the failure of materials and structures are paid high attention in human activities. For this reason, the fracture mechanics can be considered today one of the most important research fields in engineering. The attempts to predict the failure of a material are able to link different disciplines: in this dissertation, a very deep use of the statistical physics will be done in order to try to introduce the disorder of the medium into the breaking and to a give a new point of view to the fracture mechanics. In the following, we will introduce a new kind of model to evaluate the genesis of the crack: the statistical central force model. As we will see, this model tries to compute the genesis of the fracture in a medium by taking into account the presence of defects of the material that are the main cause of the differences between the critical theoretical strength of a material and the real one. This innovation introduced by this model which is difficult to find in other kinds of techniques existing today united to the fact that we try to predict the behaviour of a macro system by knowing exactly the statistical behaviour of the micro-components of the system itself (the trusses) like in complex systems happens, is the main innovation of the statistical central force model. The model consists of a truss structure in which each truss is representative of a little portion of the material. Since this model was already applied in static for a porous medium in literature, we will study it from a mathematical viewpoint and we will apply it to the study of the dynamic of a dry medium before (the applications could be for the study of the fracture in metals and composites with loads changing in time) and of a porous medium later (in order to study the fracking into soils and the fracture of the concrete). Further developments could bring us to develop the same method for the study of the spalling in the concrete because of the application of a thermal load. In the dissertation we will introduce the mathematical tools to understand this model and some simulation on generic media will be realized. This dissertation consists basically of five chapters. In chapter 1 a brief description of the state of the art will be given: we will leave from the birth of the classical elastic fracture mechanics and we will shortly talk about the fracture mechanics in a plastic field. After this we will describe two important techniques used today for the evaluation of the crack: the XFem and the Peridynamics; the first one is a numerical technique allowing the FEM to take into account the possibility to create a breaking into the material. This is done, as we will see, by adding further degrees of freedom to the finite elements. In this way a single finite element will have the possibility to “open” itself and to simulate a discontinuous field of displacements, which is the main problem concerning with FEM in calculating the fracture. The second one is a theory that postulates that each medium can be divided in particles and that each particle interacts with its own neighbours within a given horizon. From which we get the word “peri”. By this assumption it is possible to get some integro-equations that can be defined on the surfaces of the tips and of the cracks as well. In chapter 2 we will talk about the so called Fiber Bundle Model which is the basis of our statistical model. We will talk about the dry FBM that was already studied at the beginning of ’90s from a mathematical viewpoint : it consists of a bundle of fibers clamped at one edge and free to move to the other one. The model is one dimensional and it is probably one of the most naïve models to begin to study the fracture; however, despite to its simplicity, it contains an important tool: the possibility to take into account the defects of the medium by introducing the concept of variable thresholds in stress. As we will see, these thresholds will be picked up by a probability density function. Then we will apply the theory of the statistical ensembles to study one of the extensions of the FBM: the continuous fiber bundle model. This is necessary to have an idea of how the micro-components of our model, the trusses, behave in a truss structure subject to an external load. In chapter 3 we will report briefly the theory of the porous medium according to the mixture theories of De Boer. So an overview about the equations will be given and then we will discretize these equations according to the finite element technique. After this, we will briefly describe in which part of the algorithm the concept of imperfection/threshold in stress enters. We will do this for a dry medium and for a porous medium in dynamics. In chapter 4 we will report the numerical results. Some simulations in dynamics will be done both for a dry medium and for a porous medium. Furthermore we will introduce in the end a new damage law that will have a precise statistical meaning: it will be the average among all the possible realizations of the constitutive laws of our truss structure and for a big number of trusses, it will become the constitutive behaviour of our structure from which to get the damage law. And this result will take into account the disorder of the medium. In chapter 5 we will talk about a controversial argument: the Self Organized Criticality (SOC) that was sticked in previous papers to the statistical central model. We will try to understand what SOC is and if our system with our algorithm to compute the fracture gets the necessary and sufficient conditions to enter into the set of the SOC systems. At the end of our journey we will have hopefully done a first step into the description of a new numerical tool to evaluate the crack into a generic medium without needing an initial discontinuity to develop the crack itself. The next steps will be to validate this technique for existing materials and to compare it to other numerical tools like XFem or Peridynamics. After this, the future will be to extend the technique passing from trusses to 2D elements.<br>Fracture mechanics plays an important role in the material science, structure design and industrial production due to the failure of materials and structures are paid high attention in human activities. For this reason, the fracture mechanics can be considered today one of the most important research fields in engineering. The attempts to predict the failure of a material are able to link different disciplines: in this dissertation, a very deep use of the statistical physics will be done in order to try to introduce the disorder of the medium into the breaking and to a give a new point of view to the fracture mechanics. In the following, we will introduce a new kind of model to evaluate the genesis of the crack: the statistical central force model. As we will see, this model tries to compute the genesis of the fracture in a medium by taking into account the presence of defects of the material that are the main cause of the differences between the critical theoretical strength of a material and the real one. This innovation introduced by this model which is difficult to find in other kinds of techniques existing today united to the fact that we try to predict the behaviour of a macro system by knowing exactly the statistical behaviour of the micro-components of the system itself (the trusses) like in complex systems happens, is the main innovation of the statistical central force model. The model consists of a truss structure in which each truss is representative of a little portion of the material. Since this model was already applied in static for a porous medium in literature, we will study it from a mathematical viewpoint and we will apply it to the study of the dynamic of a dry medium before (the applications could be for the study of the fracture in metals and composites with loads changing in time) and of a porous medium later (in order to study the fracking into soils and the fracture of the concrete). Further developments could bring us to develop the same method for the study of the spalling in the concrete because of the application of a thermal load. In the dissertation we will introduce the mathematical tools to understand this model and some simulation on generic media will be realized. This dissertation consists basically of five chapters. In chapter 1 a brief description of the state of the art will be given: we will leave from the birth of the classical elastic fracture mechanics and we will shortly talk about the fracture mechanics in a plastic field. After this we will describe two important techniques used today for the evaluation of the crack: the XFem and the Peridynamics; the first one is a numerical technique allowing the FEM to take into account the possibility to create a breaking into the material. This is done, as we will see, by adding further degrees of freedom to the finite elements. In this way a single finite element will have the possibility to “open” itself and to simulate a discontinuous field of displacements, which is the main problem concerning with FEM in calculating the fracture. The second one is a theory that postulates that each medium can be divided in particles and that each particle interacts with its own neighbours within a given horizon. From which we get the word “peri”. By this assumption it is possible to get some integro-equations that can be defined on the surfaces of the tips and of the cracks as well. In chapter 2 we will talk about the so called Fiber Bundle Model which is the basis of our statistical model. We will talk about the dry FBM that was already studied at the beginning of ’90s from a mathematical viewpoint : it consists of a bundle of fibers clamped at one edge and free to move to the other one. The model is one dimensional and it is probably one of the most naïve models to begin to study the fracture; however, despite to its simplicity, it contains an important tool: the possibility to take into account the defects of the medium by introducing the concept of variable thresholds in stress. As we will see, these thresholds will be picked up by a probability density function. Then we will apply the theory of the statistical ensembles to study one of the extensions of the FBM: the continuous fiber bundle model. This is necessary to have an idea of how the micro-components of our model, the trusses, behave in a truss structure subject to an external load. In chapter 3 we will report briefly the theory of the porous medium according to the mixture theories of De Boer. So an overview about the equations will be given and then we will discretize these equations according to the finite element technique. After this, we will briefly describe in which part of the algorithm the concept of imperfection/threshold in stress enters. We will do this for a dry medium and for a porous medium in dynamics. In chapter 4 we will report the numerical results. Some simulations in dynamics will be done both for a dry medium and for a porous medium. Furthermore we will introduce in the end a new damage law that will have a precise statistical meaning: it will be the average among all the possible realizations of the constitutive laws of our truss structure and for a big number of trusses, it will become the constitutive behaviour of our structure from which to get the damage law. And this result will take into account the disorder of the medium. In chapter 5 we will talk about a controversial argument: the Self Organized Criticality (SOC) that was sticked in previous papers to the statistical central model. We will try to understand what SOC is and if our system with our algorithm to compute the fracture gets the necessary and sufficient conditions to enter into the set of the SOC systems. At the end of our journey we will have hopefully done a first step into the description of a new numerical tool to evaluate the crack into a generic medium without needing an initial discontinuity to develop the crack itself. The next steps will be to validate this technique for existing materials and to compare it to other numerical tools like XFem or Peridynamics. After this, the future will be to extend the technique passing from trusses to 2D elements.

Customized cellular material is a relatively new area made possible by advancements in rapid manufacturing technologies. Rapid manufacturing is ideal for the production of customized cellular structure, especially on the meso scale, due to the size and complexity of the design. The means to produce this type of structure now exist, but the processes to design the structure are not well developed. The manual design of customized cellular material is not realistic due to the large number of features. Currently there are few tools available that aid in the design of this type of material. In this thesis, an automated tool to design customized cellular structure is presented.

AbstractDue to the additional design freedom and manufacturing possibilities of additive manufacturing compared to traditional manufacturing, topology optimization via mathematical optimization gained importance in the initial design of complex high-strength lattice structures. We consider robust topology optimization of truss-like space structures with multiple loading scenarios. A typical dimensioning method is to identify and examine a suspected worst-case scenario using experience and component-specific information and to incorporate a factor of safety to hedge against uncertainty. We present a quantified programming model that allows us to specify expected scenarios without having explicit knowledge about worst-case scenarios, as the resulting optimal structure must withstand all specified scenarios individually. This leads to less human misconduct, higher efficiency and, thus, to cost and time savings in the design process. We present three-dimensional space trusses with minimal volume that are stable for up to 100 loading scenarios. Additionally, the effect of demanding a symmetric structure and explicitly limiting the diameter of truss members in the model is discussed.

AbstractThe trend towards flexible, agile, and resource-efficient production systems requires a continuous development of processes as well as of tools in the area of forming technology. To create load-adjusted and weight-optimized tool structures, we present an overview of a new algorithm-driven design optimization workflow based on mixed-integer linear programming. Loads and boundary conditions for the mathematical optimization are taken from numerical simulations. They are transformed into time-independent point loads generating physical uncertainty in the parameters of the optimization model. CAD-based mathematical optimization is used for topology optimization and geometry generation of the truss-like structure. Finite element simulations are performed to validate the structural strength and to optimize the shape of lattice nodes to reduce mechanical stress peaks. Our algorithm-driven design optimization workflow takes full advantage of the geometrical freedom of additive manufacturing by considering geometry-based manufacturing constraints. Depending on the additive manufacturing process, we use lower and upper bounds on the diameter of the members of a truss and the associated yield strengths. An additively manufactured flexible blank holder demonstrates the algorithm-driven topology design optimization.

A new technology method is adapted to manufacture carbon fiber lattice sandwich beam with pyramidal truss core. The flat crush test experiment is to test the resistance to compression of the carbon fiber sandwich plate with pyramidal truss core. The result shows that after the pressure head contact the specimens adequately, and the stiffness of structure is the maximum. If the load is continuing increase, the pyramidal truss core may be destroyed, and both sides of the carbon fiber panel begin tottering. It emerges permanent deformation on the structures after an uninstall. The three-point bending test of lattice sandwich beam referred to ASTM C393-00 is designed to research the mechanical properties of face sheet and pyramidal truss core of lattice sandwich beam with theoretical analysis. Load-deflection curves of the middle of lattice sandwich beam in long span and in short span tests are retained, which are applied to obtain flexure stiffness of face sheet and shear strength of pyramidal truss core. It is found that span length has some influence on damage modes of lattice sandwich beam with pyramidal truss core. Debonding between face sheet and lattice core occurs when span is larger and core collapse appears when span is smaller. Crack expansion and fracture of resin base also both emerge in these two damage modes and the crack expansion consists of two different types which are crack expansion inside the resin base and crack expansion from the indenter to the support. Contrast with other lattice sandwich beam with similar or different shapes of core in the other references, the mechanical properties of this lattice sandwich beam by this new fabrication have obvious advantage at the same relative density.

Cellular materials, often called lattice materials, are increasingly receiving attention for their ultralight structures with high specific strength, excellent impact absorption, acoustic insulation, heat dissipation media and compact heat exchangers. In alignment with emerging additive manufacturing (AM) technology, realization of the structural applications of the lattice materials appears to be becoming faster. Considering the direction dependent material properties of the products with AM, by directionally dependent printing resolution, effective moduli of lattice structures appear to be directionally dependent. In this paper, we develop a constitutive model of a lattice structure, which is an octet-truss with a base material having an orthotropic material property considering AM. One case study is conducted with an orthotropic property of a base material in 3D Printing. A polyjet based 3D printing material having an orthotropic property with a 9% difference in the principal direction provides difference in the axial and shear moduli in the octet-truss by 2.3 and 4.6%.

Consider an ontology T where every axiom is labeled with an element of a lattice (L, ≤). Then every element l of L determines a sub-ontology Tl, which consists of the axioms of T whose labels are greater or equal to l. These labels may be interpreted as required access rights, in which case Tl is the sub-ontology that a user with access right l is allowed to see, or as trust levels, in which case Tl consists of those axioms that we trust with level at least l. Given a consequence α (such as a subsumption relationship between concepts) that follows from the whole ontology T, we want to know from which of the sub-ontologies Tl determined by lattice elements l the consequence α still follows. However, instead of reasoning with Tl in the deployment phase of the ontology, we want to pre-compute this information during the development phase. More precisely, we want to compute what we call a boundary for α, i.e., an element μα of L such that α follows from T l iff l ≤ μα. In this paper we show that, under certain restrictions on the elements l used to define the sub-ontologies, such a boundary always exists, and we describe black-box approaches for computing it that are generalizations of approaches for axiom pinpointing in description logics. We also present first experimental results that compare the efficiency of these approaches on real-world ontologies.